Myxomatosis is a viral infection which is fatal to rabbits,
although it is treatable in tame rabbits if caught early enough,and
it was first reported in Uruguay, South America, in 1898. Attempts to use
it as a means of controlling wild rabbits have resulted in epidemics. It
can be transmitted by any biting or blood-sucking insect, such as a flea
or a mosquito.

Insect vectors form a very important method of
transmission. A wide number of mosquitoes, fleas, ticks, mites and lice
have been shown to be vectors. The insects can feed on the blood of the
infected rabbit or more easily on the exposed area of skin lesions. Further
more, unlike infected rabbits which die after about ten days after which
the possibility of contact infection is reduced, it has been shown that
mosquitoes can carry a virus capable of re-infecting rabbits for up to 6
weeks. Rabbit fleas, particularly Spilopsyllus cuniculi, can
act a reservoir of infection for several months after rabbits have deserted
a burrow.

Taking into account the range of mosquitoes this
allows transmission of the myxoma virus over greater areas than are usually
travelled by the rabbits alone. This allows the spread of the virus to take
place between colonies of rabbits, and in the case of the fleas, allows
rabbits from a different colony to become infected be entering a warren
where all the occupants have been killed by myxomatosis some months previously.

The symptoms of myxomatosis include a watery discharge from
the eyes and swelling of the eyelids and nose. Death follows in about two
weeks. Since 1952, it has been illegal to spread the disease in Britain
by the use of infected animals. Nevertheless, an epidemic broke out in Britain
in 1953. It has been estimated that 99% of the rabbit population of over
60 million died in this epidemic.

Apart from killing off large numbers of the rabbit population,
myxomatosis had an indirect effect on the rabbit's predators. The buzzard
population in particular suffered a serious setback. Grass on downlands
quickly became long since there were fewer rabbits, and attacks by foxes
on hen roosts and game became more frequent. The disease is still liable
to flare up in some areas, although there are indications that many rabbits
are now immune.